Recent nationally reported incidents of violence (Columbine, Atlanta) have suggested that negative emotional states arising from environmental stressors (e.g., peer rejection, financial difficulties) can prompt some individuals to act out violently against others not responsible for their distress. Self-report and experimental research has confirmed a general emotional priming of aggression (Berkowitz, 1990; Geen, 1990; Moyer, 1976; Rotton, 1979; Bell & Baron, 1976). Other research supports a relationship between negative emotional traits and reactive forms of aggressive behavior (Caprara et al., 1983; Netter, et al., 1998). Emphasis should be placed on examining cognitive-emotional interactions as mechanisms underlying risk for chronic aggression (Berkowitz, 1994). Preliminary evidence suggests that heightened aggression in stress-reactive individuals may result from the experience of prolonged periods of negative emotions (Verona, Patrick, & Lang, 2002) and the tendency to ruminate or experience recurrent negative thinking about past events (Caprara, et al., 1987; Rusting & Nolen-Hoeksema, 1998). The current project will examine the interacting impact of prolonged emotional and cognitive experiences on laboratory aggressive behavior (via a Buss paradigm) among individuals exhibiting varying levels of negative emotional traits. Simultaneous recording of on-going negative emotional state (indexed via acoustic startle reactivity), autonomic nervous system activity, and aggressive responses will occur during experimental task blocks including a high stress or low stress condition. Participants' autonomic responses will also be recorded during a post-task "recovery" period, and subsequently, aggressive responses will be gauged during a post-recovery final block. Self-report measures of rumination will also be administered. It is expected that highly stress-reactive persons will experience prolonged (tonic) negative emotional arousal when exposed to an on-going stressor, as well as for a period of time after the end of the stressor. It is hypothesized that the tendency to "hold on" to negative emotions and thoughts will be directly related to participants' concurrent (during experimental blocks) and subsequent (during the post-recovery block) aggressive responses toward a confederate.